The Binding of Isaac: Four Souls

The game started development around 2017 when Studio71 US approached McMillen; Studio71 was in the process of making the Cyanide & Happiness card game, Joking Hazard, and had asked McMillen if he was interested in a board game variant of The Binding of Isaac. At that point, McMillen was still focused on developing The End Is Nigh and The Legend of Bum-bo, and declined the offer.[1] About a year later, McMillen had gotten the flu, and during his off-time, came up with a card game variant for The Binding of Isaac. After prototyping enough of the game for about two months, he recontacted Studio71 to work out the fuller details for the game.[2]

Studio71 had suggested the Kickstarter route for gaining funding for the game, as they had used that successfully for Joking Hazard. McMillen was wary, knowing that digital-based Kickstarters could fail, but agreed to using it as long as they had a nearly-ready product to be sold at the start of the Kickstarter, and that he could expand on the game by adding new cards when extended Kickstarter goal tiers were met.[2] Leading up to the Kickstarter in June 2018, McMillen had teased a new Isaac-themed game, and named it on June 25, 2018.[3] The Kickstarter, revealing that this was a card game, was launched two days later; within only a few hours of the launch of the campaign, the project was successfully funded, receiving its goal of $50,000 within the first 1.5 hours.[4] The Kickstarter ended with 38,335 backers pledging a total of $2,650,875. [5]

The basic edition contains eleven characters, their starting items, 107 monster cards, 104 loot cards, 105 treasure cards, 3 bonus soul cards for advanced play, a six sided die, an eight sided die, 100 pennies, and the rulebook. A gold box edition of the game includes an expansion pack with 99 cards, including a random foil card, four characters and their respective starting items, 30 monster cards, 30 loot cards, and 30 treasure cards.[4] The game began shipping to backers in December 2018.